Modbus protocol for SCADA in SCADA systems - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the Modbus function code for reading coils.

SCADA systems

modbus_request = {"function_code": [1], "address": 0x0013, "quantity": 19}

Drag options to blanks, or click blank then click option'

A0x01

B0x03

C0x10

D0x05

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0x03 instead of 0x01 for reading coils.

The Modbus function code 0x01 is used to read coils (digital outputs).

2fill in blank

medium

Complete the code to specify the Modbus register type for holding registers.

SCADA systems

register_type = "[1]"

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Acoil

Bholding_register

Cinput_register

Ddiscrete_input

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing input_register with holding_register.

Holding registers are used to store data that can be read or written. The correct type is holding_register.

3fill in blank

hard

Fix the error in the Modbus RTU frame checksum calculation.

SCADA systems

checksum = calculate_crc([1])

Drag options to blanks, or click blank then click option'

Amodbus_frame

Bmodbus_frame[-2:]

Cmodbus_frame[2:]

Dmodbus_frame[:-2]

Attempts:

3 left

💡 Hint

Common Mistakes

Including checksum bytes in calculation causing errors.

The checksum is calculated over the entire frame except the last two bytes which contain the checksum itself. So use modbus_frame[:-2].

4fill in blank

hard

Fill both blanks to create a Modbus TCP request header with transaction ID and protocol ID.

SCADA systems

header = [1].to_bytes(2, 'big') + [2].to_bytes(2, 'big') + b'\x00\x06'

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Atransaction_id

Bprotocol_id

Cunit_id

Dlength

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping protocol_id and transaction_id.

The Modbus TCP header starts with a 2-byte transaction ID and a 2-byte protocol ID. So the first blank is transaction_id and the second is protocol_id.

5fill in blank

hard

Fill all three blanks to build a dictionary comprehension filtering coils with status ON.

SCADA systems

active_coils = {addr: status for addr, status in coils.items() if status [1] [2] and addr [3] 100}

Drag options to blanks, or click blank then click option'

A==

BTrue

C<

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using != True or wrong comparison operators.

The comprehension filters coils where status is True (ON) and address is less than 100. So the blanks are ==, True, and <.